The flyash (solid and hollow; also known as cenospheres), the waste byproduct of the thermal power plants, comprising the silica (SiO2), alumina (Al2O3), and oxides of iron, calcium (CaO), magnesium, and toxic heavy metals such as arsenic, lead, and cobalt, has been environmentally hazardous and pose major disposal problems worldwide. The first major drawback utilizing this waste material is that, innovative value-added products based on the flyash for the industrial applications are currently lacking. The second major drawback in utilizing this waste material is that, the new process for modifying the surface of flyash particles to make them suitable for the industrial applications are limited—(http://edugreen.teri.res.in/explore/air/flyash.htm).
A new electroless method for depositing the conducting metals such as copper (Cu) and silver (Ag) on the surface of flyash particles has been described. The prior art involves adsorbing tin(II)-ions (Sn2+) on the surface of flyash particles by stirring them in an acidic aqueous bath of tin(II) chloride (SnCl2) (conventional surface-sensitization bath).SnCl2→Sn2++2Cl−  (1)
The surface-sensitized flyash particles are then stirred in an aqueous acidic solution of palladium(II) chloride (PdCl2) (conventional surface-activation bath) to activate the surface of flyash particles with the Pd clusters.Sn2++Pd2+→Pd0+Sn4+  (2)
The surface-activated flyash particles are then stirred in a conventional electroless bath consisting of aqueous basic solution with dissolved metal precursor such as nitrates, sulfates; or chlorides of a metal, a stabilizer such as sodium potassium tartrate (NaKC4H4O6), pH controller such as sodium hydroxide (NaOH), and a reducing agent such as formaldehyde (HCHO) to coat Cu or Ag to produce the surface-modified flyash-based products for industrial applications.Cu2++2e−→Cu0  (3)
A reference may be made to the deposition of Cu on mica, graphite, Al2O3, SiO2, and titania (TiO2) particles via conventional electroless process, which Utilize the conventional Sn—Pd catalyst system and Cu as a self-activator (S. Shukla and S. Seal, “Electroless Copper Coating of Zirconia utilizing Palladium Catalyst”, J. Am. Ceram. Soc. 86 (2) 279-285 (2003); S. Shulda, S. Seal, Z. Rahman, and K. Scammon, “Electroless Copper Coating of Cenospheres using Silver Nitrate Activator”, Mater. Lett. 57, 151-156 (2002); J. Akesson, S. Seal, S. Shulda, and Z. Ralunan, “Copper Plating Process Control by SEM”, Adv. Mater. Processes (AMP) 160 (2), 33-35 (2002); S. Shulda, S. Seal, S. Schwarz, and D. Thou, “Synthesis and Characterization of Nanocrystalline Silver Coating of Flyash Cenosphere Particles by Electroless Process”, J. Nanosci. Nanotech. 1, 417-424 (2001); S. Shulda, S. Seal, J. Akesson, R. Oder, R. Carter, and Z. Rahman, “Study of Mechanism of Electroless Copper Coating of Fly-Ash Cenosphere Particles”, App. Surf. Sci. 181 (1-2) 35-50 (2001).
The third major drawback of the prior art is that, the Conventional Sn—Pd catalyst system is very costly. The forth major drawback of the prior art is that, there exists no alternative mechanism to sensitize the surface of flyash particles to coat them with metals such as Cu and Ag. The fifth major drawback of the prior art is that, there exists no alternative mechanism to activate the surface of flyash particles to coat them with metals such as Cu and Ag. (D. Deonath and P. K. Rohatgi, “Cast Aluminium Alloy Composites Containing Copper-Coated Ground Mica Particles”, J. Mater. Sci. 16 (6), 1599-1606 (1981); W. Lu, V. S. Donepudi, J. Prakash, J. Liu, and K. Amine, “Electrochemical and Thermal Behavior of Copper Coated Type MAG-20 Natural Graphite”, Electrochim. Acta 47 (10), 1601-1606 (2002); J. F. Silvain, J. L. Bobet, and J. M. Heintz, “Electroless Deposition of Copper onto Alumina Sub-Micronic Powders and Sintering”, Composites A 33 (10), 1387-1390 (2002); Y. Kobayashi, Y. Tadaki, D. Nagao, and M. Konno, “Deposition of Gold Nanoparticles on Silica Spheres by Electroless Metal Plating Technique”, J. Colloid Interface Sci. 283 (2), 601-604 (2005); K. Gopalcumar, C. Pavithran, and P. K. Rohatgi, “Preparation of Copper Coated Titania Particles for Composites”, J. Mater. Sci. 15 (6), 1588-1592 (1980); K. Gopakumar; T. P. Murali, and P. K. Rohatgi, “Metat-Shell Char Particulate Composites using Copper Coated Particles”, J. Mater. Sci. 17 (4); 1041-1048 (1982); K. G. K. Warrier and P. K. Rohatgi, “Mechanical, Electrical and Electrical Contact Properties of Copper Titania Composites”, J. Powder Metall. 29 (1), 65 (1986).